Curable compositions based on functional polysiloxanes

ABSTRACT

Curable compositions containing novel polysiloxanes having various reactive functional groups are disclosed. The curable compositions are useful as both ambient-cured and thermally-cured coating compositions which provide such properties as excellent appearance, mar resistance, acid etch resistance, adhesion, pot life, improved tack time, mar resistance and corrosion resistance.

This is a division of application Ser. No. 08/904,597, filed Aug. 1,1997, now U.S. Pat. No. 5,939,491.

BACKGROUND OF THE INVENTION

Polysiloxane polyols are well known in the art. Japanese PatentPublication 48-19941 describes polysiloxane polyols which are obtainedby the dehydrogenation reaction between a polysiloxane hydride and analiphatic polyhydric alcohol or polyoxyalkylene alcohol to introduce thealcoholic hydroxy groups onto the polysiloxane backbone. In practice,however, it is difficult to obtain an industrially significant yield ofsuch polysiloxane polyols because such a hydrosilylation reactionreadily gels. Another problem encountered with this hydrosilylationreaction is the difficulty in obtaining a solvent capable of dissolvingboth reactants. Strongly hydrophilic alcohols such as polyglycerols arehighly soluble in alcohols and water, but insoluble in hydrocarbonsolvents. Polysiloxanes, however, are generally only soluble inhydrocarbon solvents such as toluene or n-hexane.

U.S. Pat. No. 4,431,789 to Okazaki et al. discloses a polysiloxanepolyol which is obtained by the hydrosilylation reaction between apolysiloxane containing silicon hydride and a polyglycerol compoundhaving an aliphatically unsaturated linkage in the molecule. Examples ofsuch polyglycerol compounds are those obtained by the reaction of allylalcohol and glycidol or by the reaction of diglycerin and allyl glycidylether. This reaction, a so-called hydrosilylation reaction, is theaddition reaction between an organosilicon compound having a hydrogenatom directly bonded to the silicon atom, i.e., a polysiloxane hydride,and an organic compound having aliphatic unsaturation in the moleculecarried out in the presence of a catalytic amount of a Group VIII noblemetal. The hydrosilylation reaction can proceed readily in the presenceof an alcoholic solvent which can dissolve both reactants. The resultingpolysiloxane polyols are useful as non-ionic surface active agents.However, the polysiloxane polyols have limited compatibility withorganic resins and solvents which restricts their use in solvent-bornecoatings.

U.S. Pat. No. 5,260,469 discloses butoxylated polysiloxane polyols whichare disclosed as being useful in cosmetics. U.S. Pat. No. 5,248,789discloses epoxy functional polysiloxanes which are formed by reacting apolysiloxane-containing silicon hydride with allyl glycidyl ether.

The prior art references do not teach further reacting the hydroxylgroups of the polysiloxane polyols with other groups to provide variousreactive functional groups pendant from the polysiloxane backbone. Suchreactive functional groups allow incorporation of the polysiloxanemoiety into curable compositions which can contain a variety of reactivecomponents, including a variety of curing agents. There is no indicationin the references of using either the polysiloxane polyols or theirderivatives as major components in curable compositions.

SUMMARY OF THE INVENTION

The present invention relates to curable compositions comprising anorganic polysiloxane which can contain a variety of reactive functionalgroups and a curing agent which contains functional groups reactive withthe functional groups of the polysiloxanes. Such curable compositionsare particularly useful in coating compositions which are curable atboth ambient and thermal cure conditions where they provide suchexcellent properties as increased pot-life, improved tack-time,adhesion, mar resistance and acid etch resistance.

The curable composition of the present invention comprises an organicpolysiloxane containing reactive functional groups, said polysiloxanehaving the following general structure: ##STR1## where m is at least 1;m' is 0 to 50; n is 0 to 50; R is selected from the group consisting ofOH and monovalent hydrocarbon groups connected to the silicon atoms;R^(a) has the following structure:

    (IV) R.sub.1 --O--X                                        (IV)

wherein R₁ is alkylene, oxyalkylene or alkylene aryl; and X is a moietycontaining a functional group selected from the group consisting of OH,COOH, NCO, carboxylate such as ester, carbonate and anhydride, primaryamine, secondary amine, amide, carbamate and epoxy functional groups;and a component which contains functional groups reactive with thefunctional groups of the organic polysiloxane.

Preferably, the curable composition comprises:

(a) an organic polysiloxane containing reactive functional groups, thepolysiloxane having the formula (II) or (III), where m, m', n, R, R^(a)and X are as described above;

(b) a polymer or oligomer which contains reactive functional groups; and

(c) a curing agent containing functional groups which are reactive withthe functional groups of (a) and (b). In one preferred embodiment n+mand n+m' is 2 or 3.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the curable composition of the present invention comprises:

(a) an organic polysiloxane containing reactive functional groups, thepolysiloxane having the formula (II) or (III), where m, m', n, R, R^(a)and X are as described above; and

(b) a curing agent which contains functional groups reactive with thefunctional groups of (a).

It should be appreciated that the various R groups can be the same ordifferent, and it is usually the case that the R groups will be mixedgroups or entirely monovalent hydrocarbon groups.

By monovalent hydrocarbon groups is meant organic groups containingessentially carbon and hydrogen. The hydrocarbon groups may bealiphatic, aromatic, cyclic or acyclic and may contain from 1 to 24 (inthe case of aromatic from 3 to 24) carbon atoms. Optionally, thehydrocarbon groups may be substituted with heteroatoms, typicallyoxygen. Examples of such monovalent hydrocarbon groups are alkyl,alkoxy, aryl, alkaryl or alkoxyaryl groups.

By alkylene is meant acyclic or cyclic alkylene groups having a carbonchain length of from C₂ to C₂₅. Examples of suitable alkylene groups arethose derived from propene, butene, pentene, 1-decene, isoprene, myrceneand 1-heneicosene. By oxyalkylene is meant an alkylene group containingat least one ether oxygen atom and having a carbon chain length of fromC₂ to C₂₅, preferably of from C₂ to C₄. Examples of suitable oxyalkylenegroups are those associated with trimethylolpropane monoallylether,pentaerythritol monoallylether, trimethylolpropane diallylether,polyethoxylated allyl alcohol and polypropoxylated allyl alcohol. Byalkylene aryl is meant an acyclic alkylene group containing at least onearyl group, preferably phenyl, and having an alkylene carbon chainlength of from C₂ to C₂₅. The aryl group may optionally be substituted.Suitable substituent groups may include hydroxyl, benzyl, carboxylicacid and aliphatic groups. Examples of suitable alkylene aryl groupsinclude styrene and 3-isopropenyl-α,α-dimethylbenzyl isocyanate.

Formulae (II) and (III) are diagrammatic, and it is not intended toimply that the parenthetical portions are necessarily blocks, althoughblocks may be used where desired.

In many cases the compound is more or less random, especially when morethan a few siloxane units are employed and when mixtures are used. Inthose instances where more than a few siloxane units are used and it isdesired to form blocks, oligomers are first formed and then these arejoined to form the block compound. By judicious choice of reactants,compounds having an alternating structure or blocks of alternatingstructure may be used.

Preferably, the curable composition comprises:

(a) an organic polysiloxane containing reactive functional groups, thepolysiloxane having the formula (II) or (III), where m, m', n, R, R^(a)and X are as described above;

(b) a polymer which contains reactive functional groups; and

(c) a curing agent containing functional groups which are reactive withthe functional groups of (a) and (b). In one preferred embodiment n+mand n+m' is 2 or 3.

It should be mentioned that when both (a) and (b) are present, thereactive functional groups of (a) and (b) can be the same or different,but both must be reactive with the functional groups of the curingagent. Examples of such reactive functional groups include OH, COOH,NCO, carboxylate, primary amine, secondary amine, amide, carbamate andepoxy functional groups.

THE POLYSILOXANES CONTAINING REACTIVE FUNCTIONAL GROUPS

In one preferred embodiment of the invention, X is a moiety whichcontains OH functional groups. Preferably, when X contains OH functionalgroups, at least a portion of X is a group having the followingstructure: ##STR2## More preferably, when X is a group having theformula (V), m is 2 and p is 2.

In one embodiment of the invention, X is a moiety which contains COOHfunctional groups. Preferably, when X is a group containing COOHfunctional groups, the organic polysiloxane is the reaction product ofthe following reactants:

(a) a polysiloxane polyol having the following structure: ##STR3## wherem is at least 1; m' is 0 to 50; n is 0 to 50; R is selected from thegroup consisting of H, OH and monovalent hydrocarbon groups connected tothe silicon atoms; R^(b) has the following structure:

    R.sub.1 --O--Y                                             (IX)

wherein R₁ is alkylene, oxyalkylene or alkylene aryl; and Y is H,mono-hydroxy substituted alkylene or oxyalkylene, or has the structureof formula (V) wherein p, R₂, and R₃ are as described above; and

(b) at least one polycarboxylic acid or anhydride, preferably ananhydride.

Examples of anhydrides, suitable for use in the present invention asreactant (b) immediately above include hexahydrophthalic anhydride,methyl hexahydrophthalic anhydride, phthalic anhydride, trimelliticanhydride, succinic anhydride, chlorendic anhydride, alkenyl succinicanhydride and substituted alkenyl anhydrides such as octenyl succinicanhydride and mixtures thereof.

In yet another embodiment of the invention, X is a moiety which containsepoxy functional groups. Preferably, when X is a group containing epoxyfunctional groups, the organic polysiloxane is the reaction product ofthe following reactants:

(a) a polysiloxane polyol having the structure of formula (VII) or(VIII), where m, m', n, R, R^(b) and Y are as described above for thesestructures; and

(b) at least one polyepoxide, preferably an aliphatic or cycloaliphaticpolyepoxide, or mixtures thereof.

Examples of polyepoxides suitable for use in the present invention asreactant (b) immediately above are those well known in the art, such asthose described in U.S. Pat. No. 4,681,811 at col. 4, line 52 to col. 5,line 50, hereby incorporated by reference.

In another embodiment of the invention, X is an oligomeric or polymericurethane or urea-containing material which is terminated with NCO, OH,primary amine or secondary amine functional groups. When X is such amoiety, the organic polysiloxane is the reaction product of thefollowing reactants:

(a) a polysiloxane polyol having the structure of formula (VII) or(VIII), where m, m', n, R, R^(b) and Y are as described above for thesestructures;

(b) at least one polyisocyanate; and

(c) optionally at least one compound having at least 2 active H atomsper molecule selected from the group consisting of hydroxyl, primaryamine and secondary amine.

Examples of polyisocyanates suitable for use in the present invention asreactant (b) immediately above are commonly known in the art, such asthose described in U.S. Pat. No. 4,046,729 at col. 5, line 26 to col. 6,line 28, hereby incorporated by reference. Preferred are aliphatic orcycloaliphatic diisocyanates, or mixtures thereof.

Examples of compounds having at least 2 active H atoms per molecule, arepolyols and polyamines containing primary and/or secondary amines.Examples of polyols suitable for use in the present invention asreactant (c) immediately above are well known in the art, such as thosedescribed in U.S. Pat. No. 4,046,729 at col. 7, line 52 to col. 10, line35, hereby incorporated by reference. Examples of polyamines suitablefor use in the present invention as reactant (c) immediately above arewell known in the art, such as those described in U.S. Pat. No.4,046,729 at col. 6, line 61 to col. 7, line 32, and in U.S. Pat. No.3,799,854 at col. 3, lines 13 to 50, both hereby incorporated byreference.

Reaction conditions and the ratio of the reactants (a), (b) and (c) areselected so as to form the desired terminal group.

In yet another embodiment of the invention, X is an oligomeric orpolymeric ester-containing material which is terminated with OH or COOHfunctional groups. When X is such a group, the organic polysiloxane isthe reaction product of the following reactants:

(a) a polysiloxane polyol having the structure of formula (VII) or(VIII), where m, m', n, R, R^(b) and Y are as described above for thesestructures;

(b) at least one COOH containing group; and

(c) at least one organic polyol.

Examples of COOH containing groups suitable for use in the presentinvention as reactant (b) immediately above are carboxylic acid groupcontaining polymers well known in the art, such as those described inU.S. Pat. No. 4,681,811 at co. 6, line 38; col. 7, line 33; col. 7, line47; and col. 8, line 2, hereby incorporated by reference. Preferred arealiphatic and cycloaliphatic polycarboxylic acids and mixtures thereof.

Examples of organic polyols suitable for use in the present invention asreactant (c) immediately above are polymeric polyols well known in theart, such as those described in U.S. Pat. No. 4,798,746 at col. 3, line20 to col. 5, line 61, hereby incorporated by reference.

Reaction conditions and the ratio of the reactants (a), (b) and (c) areselected so as to form the desired terminal group.

THE CURING AGENTS

Aminoplast resins and phenoplast resins and mixtures thereof, as curingagents for OH and COOH, amide and carbamate functional group containingmaterials are well known in the art. Examples of aminoplast andphenoplast resins suitable as curing agents in the curable compositionsof the present invention are those described in U.S. Pat. No. 3,919,351at col. 5, line 22 to col. 6, line 25, hereby incorporated by reference.

Polyisocyanates and blocked polyisocyanates as curing agents for OH andprimary and/or secondary amino group containing materials are well knownin the art. Examples of polyisocyanates and blocked isocyanates suitablefor use as curing agents in the curable compositions of the presentinvention are those described in U.S. Pat. No. 4,546,045 at col. 5,lines 16 to 38; and in U.S. Pat. No. 5,468,802 at col. 3, lines 48 to60, both hereby incorporated by reference.

Anhydrides as curing agents for OH and primary and/or secondary aminogroup containing materials are well known in the art. Examples ofanhydrides suitable for use as curing agents in the curable compositionsof the present invention are those described in U.S. Pat. No. 4,798,746at col. 10, lines 16 to 50; and in U.S. Pat. No. 4,732,790 at col. 3,lines 41 to 57, both hereby incorporated by reference.

Polyepoxides as curing agents for COOH functional group containingmaterials are well known in the art. Examples of polyepoxides suitablefor use as curing agents in the curable compositions of the presentinvention are those described in U.S. Pat. No. 4,681,811 at col. 5,lines 33 to 58, hereby incorporated by reference.

Polyacids as curing agents for epoxy functional group containingmaterials are well known in the art. Examples of polyacids suitable foruse as curing agents in the curable compositions of the presentinvention are those described in U.S. Pat. No. 4,681,811 at col. 6, line45 to col. 9, line 54, hereby incorporated by reference.

Polyols, that is, material having an average of two or more hydroxylgroups per molecule, can be used as curing agents for NCO functionalgroup containing materials and anhydrides and esters and are well knownin the art. Examples of said polyols are those described in U.S. Pat.No. 4,046,729 at col. 7, line 52 to col. 8, line 9; col. 8, line 29 tocol. 9, line 66; and in U.S. Pat. No. 3,919,315 at col. 2, line 64 tocol. 3, line 33, both hereby incorporated by reference.

Polyamines can also be used as curing agents for NCO functional groupcontaining materials and for carbonates and unhindered esters and arewell known in the art. Examples of polyamines suitable for use as curingagents in the curable compositions of the present invention are thosedescribed in U.S. Pat. No. 4,046,729 at col. 6, line 61 to col. 7, line26, hereby incorporated by reference.

POLYMERS AND OLIGOMERS CONTAINING FUNCTIONAL GROUPS

The curable coating compositions of the present invention can furtherinclude additional components such as hydroxyl or carboxylicacid-containing acrylic copolymers and hydroxyl or carboxylicacid-containing polyester polymers and oligomers and isocyanate orhydroxyl-containing polyurethane polymers, or amine orisocyanate-containing polyureas which can enhance cure rate, appearanceand other physical properties of the cured coating.

The acrylic polymers, if used, are typically copolymers of acrylic acidor methacrylic acid or hydroxyalkyl esters of acrylic or methacrylicacid such as hydroxyethyl methacrylate or hydroxypropyl acrylate withone or more other polymerizable ethylenically unsaturated monomers suchas alkyl esters of acrylic acid including methyl methacrylate and2-ethyl hexyl acrylate, and vinyl aromatic compounds such as styrene,alpha-methyl styrene and vinyl toluene. The ratio of reactants andreaction conditions are selected to result in an acrylic polymer withpendant hydroxyl or carboxylic acid functionality.

Besides acrylic polymers, the curable coating composition of the presentinvention can contain a polyester polymer or oligomer. Such polymers maybe prepared in a known manner by condensation of polyhydric alcohols andpolycarboxylic acids. Suitable polyhydric alcohols include ethyleneglycol, neopentyl glycol, trimethylol propane and pentaerythritol.

Suitable polycarboxylic acids include adipic acid, 1,4-cyclohexyldicarboxylic acid and hexahydrophthalic acid. Besides the polycarboxylicacids mentioned above, functional equivalents of the acids such asanhydrides where they exist or lower alkyl esters of the acids such asthe methyl esters may be used. Also, small amounts of monocarboxylicacids such as stearic acid may be used.

Hydroxyl-containing polyester oligomers can be prepared by reacting ananhydride of a dicarboxylic acid such as hexahydrophthalic anhydridewith a diol such as neopentyl glycol in a 1:2 molar ratio.

Where it is desired to enhance air-drying, suitable drying oil fattyacids may be used and include those derived from linseed oil, soya beanoil, tall oil, dehydrated castor oil or tung oil.

The polyesters are made to contain free terminal hydroxyl and/orcarboxyl groups which are available for further crosslinking reactions.

Polyurethane polymers containing terminal isocyanate or hydroxyl groupsmay also be used. The polyurethane polyols or NCO-terminatedpolyurethanes which can be used are those prepared by reacting polyolsincluding polymeric polyols with polyisocyanates. Thepolyurea-containing terminal isocyanate or primary or secondary aminegroups which can be used are those prepared by reacting polyaminesincluding polymeric polyamines with polyisocyanates. Thehydroxyl/isocyanate or amine/isocyanate equivalent ratio is adjusted andreaction conditions selected to obtain the desired terminal group.Examples of suitable polyisocyanates are those described in U.S. Pat.No. 4,046,729 at column 5, line 26 to column 6, line 28, herebyincorporated by reference. Examples of suitable polyols are thosedescribed in U.S. Pat. No. 4,046,729 at column 7, line 52 to column 10,line 35, hereby incorporated by reference. Examples of suitablepolyamines are those described in U.S. Pat. No. 4,046,729 at column 6,line 61 to column 7, line 32 and in U.S. Pat. No. 3,799,854 at column 3,lines 13 to 50, both hereby incorporated by reference.

The coating compositions of the invention can be pigmented orunpigmented. Suitable pigments for color coats include opaque,transparent and translucent pigments generally known for use in coatingapplications. When pigment is used, it typically present in thecomposition in amounts such that the pigment to binder ratio is fromabout 0.03 to 6.0:1.

In addition to the foregoing components, the coating compositions of theinvention may include one or more optional ingredients such asplasticizers, anti-oxidants, light stabilizers, mildewcides andfungicides, surfactants and flow control additives or catalysts as arewell known in the art.

The components present in the curable coating composition of the presentinvention generally are dissolved or dispersed in an organic solvent.Organic solvents which may be used include, for example, alcohols,ketones, aromatic hydrocarbons, glycol ethers, esters or mixturesthereof.

As aforementioned, the curable compositions are particularly useful ascoating compositions. Whether the coating compositions are cured atambient or thermal conditions is dependent upon the reactive functionalgroups of the organic polysiloxane component, the optional polymer oroligomer and the curing agent component. The curable compositions of theinvention can be pigmented or unpigmented.

Suitable pigments for color coats include opaque, transparent andtranslucent pigments generally known for use in coating applications.Examples include titanium dioxide, zinc oxide, antimony oxide, ironoxide, carbon black and phthalocyanine blue. Metallic pigments such asaluminum flake and metal oxide-coated micas can also be used. Thecoatings may also contain extender pigments such as calcium carbonate,clay, silica, talc, etc. When pigment is used, it typically present inthe composition in amounts such that the pigment to binder ratio is fromabout 0.03 to 6.0:1.

In addition to the foregoing components, the coating compositions of theinvention may include one or more optional ingredients such asplasticizers, anti-oxidants, light stabilizers, mildewcides andfungicides, surfactants and flow control additives and suitablecatalysts as are well known in the art.

The components present in the curable coating composition of the presentinvention generally are dissolved or dispersed in an organic solvent.Organic solvents which may be used include, for example, alcohols,ketones, aromatic hydrocarbons, glycol ethers, esters or mixturesthereof. In solvent-based coating compositions, organic solvent istypically present in amounts of 5 to 80 percent by weight based on totalweight of the composition.

The functional group containing polysiloxane is generally present in thecurable coating composition of the present invention in amounts of 5 toabout 95, and preferably from about 10 to about 70 percent by weightbased on total weight of resin solids. The curing agent is generallypresent in amounts of from 5 to about 95 and preferably from about 10 toabout 90 percent by weight based on total weight of resin solids.Optional acrylic or polyester polymers can be present in amounts up to70 and preferably from about 10 to about 60 percent by weight based ontotal weight of resin solids.

The coating composition of the invention can be applied to the substrateby any conventional method such as brushing, dipping, flow coating, rollcoating, conventional spraying and electrostatic spraying. Typically,they are most often applied by spraying. Usual spray techniques andequipment for air spraying and electrostatic spraying and either manualor automatic methods can be used.

The compositions can be applied by conventional methods over a widevariety of primed and unprimed substrates such as wood, metal, glass,cloth, leather, plastics, foams and the like; however, they areparticularly useful over metal substrates.

The ambient temperature curable compositions such as those usingpolyisocyanate or polyanhydride curing agent can be cured at elevatedtemperatures to hasten the cure. An example would be forced air curingin a down draft booth at about 40° to 60° C. which is common in theautomotive refinish industry. The ambient temperature curablecompositions are usually prepared as a two (2) package system in whichthe curing agent is kept separate from the polysiloxane containing thereactive functional group. The packages are combined shortly beforeapplication.

The thermally curable compositions such as those using blockedisocyanate, aminoplast, phenoplast, polyepoxide or polyacid curing agentcan be prepared as a one package system.

The thermally curable coating compositions are cured at elevatedtemperatures, typically for 1 to 30 minutes at about 250° F. to about450° F. (121° C. to 232° C.) with temperature primarily dependent uponthe type of substrate used. Dwell time (i.e., time that the coatedsubstrate is exposed to elevated temperature for curing) is dependentupon the cure temperature used as well as wet film thickness of theapplied coating composition. For example, coated automotive elastomericparts require a long dwell time at a lower cure temperature (e.g., 30minutes/250° F. (121° C.)), while coated aluminum beverage containersrequire a very short dwell time at a very high cure temperature (e.g., 1minute/375° F. (191° C.)).

The coating compositions of the invention are particularly useful asprimers and as color and/or clear coats in color-clear compositecoatings. The compositions of the invention in the pigmented form can beapplied directly to a substrate to form a color coat. The color coat maybe in the form of a primer for subsequent application of a top coat ormay be a colored top coat. Alternately, the coating composition of theinvention can be unpigmented, in the form of a clear coat forapplication over a color coat (either a primer coat or a colored topcoat). When used as a primer coating, thicknesses of 0.4 to 4.0 mils aretypical. When used as a color top coat, coating thicknesses of about 0.5to 4.0 mils are usual, and when used as a clear coat, coatingthicknesses of about 1.5 to 4.0 mils are generally used.

In applying composite coatings using the coating composition of thepresent invention, the initially applied coating can be cured prior tothe application of the second coat. Alternatively, the coating can beapplied by a wet-on-wet technique in which the second coating is appliedto the first coating (usually after a flash time at room temperature orslightly elevated temperature to remove solvent or diluent, butinsufficient time to cure the coating) and the two coatings are co-curedin a single step.

Only one of the coatings in the composite coating needs to be based onthe coating composition of the present invention. The other coatingcomposition can be based on a film-forming system containing athermoplastic and/or thermosetting film-forming resin well known in theart such as cellulosics, acrylics, polyurethanes, polyesters includingalkyds, aminoplasts, epoxies and mixtures thereof. These film-formingresins are typically formulated with various other coatings ingredientssuch as pigments, solvents and optional ingredients mentioned above.

The following examples illustrate the invention and should not beconstrued as a limitation on the scope thereof. Unless specificallyindicated otherwise, all percentages and amounts are by weight.

EXAMPLES

Examples 1 through 6 describe the preparation of various polysiloxanespolyols useful in the present invention. Example 7 and ComparativeExample 8 describe, respectively, the preparation of clearcoatcompositions containing the polysiloxane polyol of Example 1 and acomparative coating containing only a polyester polyol with nopolysiloxane polyol. The following Table 1 illustrates advantages incoating properties such as tack-time, pot-life and solvent resistancederived from the use of the polysiloxane polyol. Example 9 andComparative Example 10 describe, respectively, the preparation of aclearcoat composition containing the polysiloxane polyol of Example 1used in the composition at an additive level, i.e., less than 10 percent based on total resin solids, and a comparable clearcoat compositioncontaining no polysiloxane polyol. The following Table 2 illustratesadvantages in mar resistance of the clearcoat composition derived fromthe use of the polysiloxane polyol at an additive level. Example 11describes the preparation of clearcoat compositions containing thepolysiloxane polyol of Example 2 (compositions 11B, 11C, and 11D) and acomparative composition, 11A, containing no polysiloxane polyol. Each ofthe compositions contained an aminoplast curing agent and were thermallycured. The following Table 3 illustrates the advantages in marresistance of the clearcoat compositions derived from the use of thepolysiloxane composition. Example 12 describes the curing of apolysiloxane containing COOH-functional groups with a polyepoxide curingagent. Example 13 describes the preparation of clearcoat compositionscontaining the polysiloxane polyols of Examples 5 and 6 and anaminoplast curing agent. The coatings were evaluated for Distinctness ofImage (DOI), gloss, mar resistance and acid etch resistance. The resultsare reported in the following Table 4. For the purposes of comparison,commercial clearcoat compositions based on acrylic polyol-aminoplastcure and on epoxy-acid cure are also reported.

Example 1

This example describes the preparation of a disiloxane tetrol, a productof the hydrosilylation of tetramethyl-disiloxane with an alkenylpolyoxyalkylene alcohol. The disiloxane tetrol was prepared from thefollowing mixture of ingredients:

    __________________________________________________________________________                   Equivalent   Parts By Weight                                   Ingredients    Weight                                                                              Equivalents                                                                          (grams)                                           __________________________________________________________________________    Charge I:      174.0 7.7    1335.7                                            Trimethylolpropane monoallylether                                             Charge II:      67.0 7.7    515.2                                             1,1,3,3-tetramethyl-disiloxane                                                Charge III:                 10  ppm                                           Chloroplatinic acid                                                           __________________________________________________________________________

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of sodium bicarbonateequivalent to 20 to 25 ppm of total monomer solids were added at ambientconditions and the temperature was gradually increased to 75° C. under anitrogen blanket. At that temperature, about 5.0% of Charge II was addedunder agitation, followed by the addition of Charge III, equivalent to10 ppm of active platinum based on total monomer solids. The reactionwas then allowed to exotherm to 95° C. at which time the remainder ofCharge II was added at a rate such that the temperature did not exceed95° C. After completion of this addition, the reaction temperature wasmaintained at 95° C. and monitored by infrared spectroscopy fordisappearance of the silicon hydride absorption band (Si--H, 2150 cm⁻¹).

Example 2

This example describes the preparation of polysiloxane tetrol, a productof the hydrosilylation of MASILWAX™ BASE siloxane with an approximatedegree of polymerization of 3 to 4, i.e., (Si--O)₃ to (Si--O)₄. Thesiloxane tetrol was prepared from the following mixture of ingredients:

    __________________________________________________________________________                   Equivalent   Parts By Weight                                   Ingredients    Weight                                                                              Equivalents                                                                          (grams)                                           __________________________________________________________________________    Charge I:      174.0 9.4    1630.0                                            Trimethylolpropane monoallylether                                             Charge II:     156.7.sup.2                                                                         9.4    1467.4                                            MASIL WAX BASE.sup.1                                                          Charge III:                 10  ppm                                           Chloroplatinic acid                                                           __________________________________________________________________________     .sup.1 Polysiloxanecontaining silicon hydride, commercially available fro     PPG Industries, Inc.                                                          .sup.2 Equivalent weight based on mercuric bichloride determination.     

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of sodium bicarbonateequivalent to 20 to 25 ppm of total monomer solids were added at ambientconditions and the temperature was gradually increased to 75° C. under anitrogen blanket. At that temperature, about 5.0% of Charge II was addedunder agitation, followed by the addition of Charge III, equivalent to10 ppm of active platinum based on total monomer solids. The reactionwas then allowed to exotherm to 95° C. at which time the remainder ofCharge II was added at a rate such that the temperature did not exceed95° C. After completion of this addition, the reaction temperature wasmaintained at 95° C. and monitored by infrared spectroscopy fordisappearance of the silicon hydride absorption band (Si--H, 2150 cm⁻¹).

Example 3

This example describes the preparation of a styrenated polysiloxanepolyol, a product of the hydrosilylation of a polysiloxane with anapproximate degree of polymerization of 34, i.e., (Si--O)₃₄. Thepolysiloxane polyol was prepared from the following mixture ofingredients:

    __________________________________________________________________________                   Equivalent   Parts By Weight                                   Ingredients    Weight                                                                              Equivalents                                                                          (grams)                                           __________________________________________________________________________    Charge I:                                                                     Alpha-methylstyrene                                                                          118.0 2.3    272.9                                             Polysiloxane (Si--O).sub.34.sup.1                                                            162.2 3.1    501.5                                             Charge II:     174.0  .97   168.0                                             Trimethylolpropane monoallylether                                             __________________________________________________________________________     .sup.1 Polysiloxane (Si--O).sub.34 containing silicon hydride.           

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I was added at ambient conditions, followed bythe addition of 135 microliters, 7.5% solution of chloroplatinic acid,equivalent to 10 ppm of active platinum based on total monomer solids.The temperature was gradually increased to 80° C. under a nitrogenblanket. The reaction was then allowed to exotherm to 151° C., thensubsequently cooled back to 80° C., at which time Charge II was addedwith 70 ppm of potassium acetate. The reaction was again allowed toexotherm to approximately 150° C. before cooling to and maintaining at95° C. while monitoring by infrared spectroscopy for disappearance ofthe silicon hydride absorption band (Si--H, 2150 cm⁻¹).

Example 4

This example describes the preparation of a polysiloxane polyol, aproduct of the hydrosilylation of a Si--H functional polysiloxane withan approximate degree of polymerization of 40, i.e., (Si--O)₄₀. Thepolysiloxane polyol was prepared from the following mixture ofingredients:

    __________________________________________________________________________                     Equivalent Parts By Weight                                   Ingredients      Weight                                                                             Equivalents                                                                         (grams)                                           __________________________________________________________________________    Charge I:                                                                     Trimethylolpropane monoallylether                                                              174.0                                                                              0.90  155.9                                             Tetraethoxyallyl alcohol                                                                       251.8.sup.1                                                                        0.90  225.6                                             Charge II:       158.48                                                                             1.38  218.46                                            Polysiloxane pre-polymer (Si--O).sub.40                                       Charge III:                 2 × 2.5                                                                     ppm                                           Chloroplatinic acid, 7.5% in i-propanol                                       __________________________________________________________________________     .sup.1 Equivalent weight based on iodine value. The material had an           equivalent weight based on hydroxyl analysis of 244.5 g/mol OH.          

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of potassium acetate equivalentto 50 ppm of total monomer solids was added at ambient conditions andthe temperature was gradually increased to 80° C. under a nitrogenblanket. At that temperature, about 10% of Charge II was added underagitation, followed by the addition of Charge III, equivalent to 2.5 ppmof active platinum based on total monomer solids. The reaction was thenallowed to exotherm to 85° C. at which time the remainder of Charge IIwas added at a rate such that the temperature did not exceed 85.5° C.After completion of this addition, a second charge of chloroplatinicacid equivalent to 2.5 ppm of active platinum based on total monomersolids was added and a minor additional exotherm was observed. Thereaction temperature was maintained at 80° C for eight hours andmonitored by silver nitrate testing for the presence of Si--H.

Example 5

This example describes the preparation of a polysiloxane polyol, aproduct of the hydrosilylation of a Si--H functional polysiloxane withan approximate degree of polymerization of 55: (Si--O)₅₅, with a mixtureof alpha-methyl styrene, trimethylolpropane monoallylether, and a fourmole ethoxylate of allyl alcohol. The polysiloxane polyol was preparedfrom the following mixture of ingredients:

    __________________________________________________________________________                     Equivalent Parts By Weight                                   Ingredients      Weight                                                                             Equivalents                                                                         (grams)                                           __________________________________________________________________________    Charge I:                                                                     Polysiloxane     104.4                                                                              4.79  500                                               Alpha-methyl styrene                                                                           118.18                                                                             1.96  232.1                                             Chloroplatinic acid, 7.5% in i-propanol                                                                   2.5 ppm                                           Charge II:                                                                    Tetraethoxy allylether                                                                         251.8.sup.1                                                                        1.84  462.6                                             Trimethylolpropane monoallylether                                                              174.0                                                                              1.84  320.1                                             __________________________________________________________________________     .sup.1 Equivalent weight from iodine value. The material had an equivalen     weight by hydroxyl value of 229.5 mg/mol indicating the presence of some      ethylene glycol.                                                         

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I was heated under a nitrogen blanket to 30° C.An exotherm brought the temperature up to about 50° C. at which pointfurther gentle heating induced an exotherm to about 140° C. Aftercooling to 85° C. an amount of potassium acetate equivalent to 50 ppm oftotal solids was added to Charge II and Charge II was then added underagitation. The rate of addition was set such that the reactiontemperature remained between 93 and 96° C. As the addition proceeded,the reaction began to cool and an additional charge of chloroplatinicacid equivalent to 1.0 ppm platinum based on total monomer weight wasadded. The reaction exhibited a secondary exotherm to 97° C. at whichtime the remainder of Charge II was added. The reaction temperature wasmaintained at 85° C. for two hours and monitored by silver nitratetesting for the disappearance of Si--H.

Example 6

This example describes the preparation of a polysiloxane polyol, aproduct of the hydrosilylation of a Si--H functional polysiloxane withan approximate degree of polymerization of 40: (Si--O)₄₀, with a fourmole butoxylate of allyl alcohol. The polysiloxane polyol was preparedfrom the following mixture of ingredients:

    __________________________________________________________________________                     Equivalent Parts By Weight                                   Ingredients      Weight                                                                             Equivalents                                                                         (grams)                                           __________________________________________________________________________    Charge I:        338.sup.1                                                                          1.30  446.2                                             Tetrabutoxy allylether                                                        Charge II:       162.77                                                                             1.00  162.3                                             Polysiloxane                                                                  Charge III:                 2 × 2.5                                                                     ppm                                           Chloroplatinic acid, 7.5% in i-propanol                                       __________________________________________________________________________     .sup.1 Equivalent weight from iodine value. The material had an equivalen     weight by hydroxyl value of 322 mg/mol indicating the presence of some        butylene glycol.                                                         

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of potassium acetate equivalentto 50 ppm of total monomer solids were added at ambient conditions andthe temperature was gradually increased to 80° C. under a nitrogenblanket. At that temperature, about 10% of Charge II was added underagitation, followed by the addition of Charge III, equivalent to 2.5 ppmof active platinum based on total monomer solids. The reaction was thenallowed to exotherm to 85° C. at which time the remainder of Charge IIwas added at a rate such that the temperature did not exceed 85.5° C.After completion of this addition, a second charge of chloroplatinicacid equivalent to 2.5 ppm of active platinum based on total monomersolids was added and a minor additional exotherm to about 92° C. wasobserved. The reaction temperature was maintained at 85° C. for eighthours and monitored by silver nitrate testing for the disappearance ofSi--H.

Example 7

This example describes the preparation of a two component clearcoatcomposition containing the polysiloxane polyol of Example 1. Thisclearcoat composition is curable at ambient conditions and suitable forautomotive refinish applications. The ingredients of Component 1, whichcontains the polysiloxane polyol, and Component 2, which contains anisocyanate curing agent, were co-blended under mild agitation justbefore spray application.

    ______________________________________                                                        Formula Weight                                                                            Weight Resin Solids                               Ingredients     (grams)     (grams)                                           ______________________________________                                        Component 1                                                                   Polysiloxane polyol of                                                                        27.2        27.2                                              Example 1                                                                     Siliconized polyester polyol.sup.1                                                            10.0        10.0                                              Reactive diluent.sup.2                                                                        4.9         4.9                                               Surface active agent.sup.3                                                                    0.46        0.46                                              Ultraviolet light absorber.sup.4                                                              1.57        1.49                                              Hindered amine light stabilizer.sup.5                                                         0.92        0.92                                              Hexyl acetate.sup.6                                                                           3.69        --                                                Ethylene glycol butyl ether                                                                   2.94        --                                                acetate.sup.7                                                                 Methyl amyl ketone                                                                            5.57        --                                                Ethyl-3-ethoxy propionate.sup.8                                                               3.69        --                                                Catalyst.sup.9  0.13        0.13                                              Component 2                                                                   Isocyanate curing agent.sup.10                                                                77.69       65.49                                             Enhancer.sup.11 5.88        0.12                                              Total           144.62      110.71                                            ______________________________________                                         .sup.1 The siliconized polyester polyol comprised of polysiloxane polyol      of Example 1, trimethylolpropane, isostearic acid, 1,4cyclohexyl              dicarboxylic acid in a 11.5/33.7/20.5/34.2 weight ratio.                      .sup.2 Oxazolidine commercially available as ZOLDINE RD20LC from Angus        Chemical.                                                                     .sup.3 Polysiloxane commercially available as BYK331 from BYK Chemie USA.     .sup.4 Commercially available as TINUVIN 384 from CibaGeigy Corp.             .sup.5 Sterically hindered tertiary amine light stabilizer commercially       available as TINUVIN 123 from CibaGeigy Corp.                                 .sup.6 Commercially available as EXXATE 600 from EXXON Chemical Co.           .sup.7 Commercially available as EKTASOLVE EB from Eastman Chemical Co.       .sup.8 Commercially available as EKTASOLVE EEP from Eastman Chemical Co.      .sup.9 Commercially available as METACURE T12 from Air Products and           Chemicals, Inc.                                                               .sup.10 Blend of hexamethylene diisocyanate trimer and the isocyanurate o     isophorone diisocyanate available as DCX61 from PPG Industries, Inc.          .sup.11 A 2% active solution of 2,4pentanedione commercially available        from PPG Industries, Inc. as DX84.                                       

Comparative Example 8

By way of comparison with Example 7, this example describes thepreparation of a two component clearcoat composition containing apolyester polyol with no polysiloxane polyol. The ingredients ofComponent 1 and Component 2, which contains an isocyanate curing agent,were co-blended under mild agitation just before spray application.

    __________________________________________________________________________                      Formula Weight                                                                         Weight Resin Solids                                Ingredients       (grams)  (grams)                                            __________________________________________________________________________    Component 1                                                                   Polyester polyol resin.sup.1                                                                    38.63    34.73                                              Reactive diluent ZOLDINE RD-20LC                                                                4.9      4.9                                                BYK-331           0.46     0.46                                               TINUVIN 384       1.57     1.49                                               TINUVIN 123       0.92     0.92                                               Hexyl acetate     3.32     --                                                 Ethylene glycol butyl ether acetate                                                             2.65     --                                                 Methyl amyl ketone                                                                              5.02     --                                                 Ethyl-3-ethoxy propionate                                                                       3.32     --                                                 METACURE T-12     0.13     0.13                                               Component 2                                                                   Isocyanate curing agent used in Example 7                                                       67.16    56.36                                              Enhancer used in Example 7                                                                      5.88     0.1                                                Total             133.98   99.1                                               __________________________________________________________________________     .sup.1 Condensate of trimethylolpropane, isostearic acid and 1,4cyclohexy     dicarboxylic acid (37.2/38.5/24.3 weight ratio); 90% solids in methyl amy     ketone.                                                                  

APR24711 test panels, available from ACT Laboratories (32 gauge coldrolled steel, coated with ED5000, an electrodepositable primer coatingcommercially available from PPG Industries, Inc.) were prepared by sprayapplying a second primer coat (GPX-5379 from PPG Industries, Inc.) andcuring at ambient conditions. An acrylic basecoat, commerciallyavailable as DELTRON® Universal Basecoat from PPG Industries, Inc., wasspray applied to primed panels using conventional spray equipment andallowed to flash at ambient conditions for 20 minutes. The clearcoatcompositions of Example 7 and Comparative Example 8 were then sprayapplied to the basecoat using conventional spray equipment. Theclearcoated test panels were then allowed to cure at ambient conditionsfor one week prior to testing.

To evaluate pot-life of the two-component clearcoats, Brookfieldviscosities, reported in centistokes per second (cps), were measuredusing a #3 spindle at 60 revolutions per minute, immediately after thetwo components were co-blended and again after one hour. Tack time, thatis the time from initial spray application to the test panel to the timeat which the applied coating is no longer sticky or tacky to the touch,was measured for each of the clearcoat compositions of Example 7 andComparative Example 8. The 20 degree gloss was measured after one weekcure at ambient temperatures using a Glossgard IIa gloss meter fromPacific Scientific. Gasoline resistance was measured after one week cureat ambient cure by soaking the coated panels in 93 octane gasoline for 3minutes and rating the coatings for softening of the film and marring.Results for the above-mentioned tests are reported in the followingTable 1.

                  TABLE 1                                                         ______________________________________                                                            Brookfield                                                                    Viscosity                                                 Clearcoat                                                                              Tack-free Time                                                                           0 hr./1 hr.                                                                            20 Degree                                                                            Gasoline                                  Composition                                                                            (min)      (cps)    Gloss  Resistance                                ______________________________________                                        Example 7                                                                              60         75/180   82     no change; no                                                                 gloss loss                                Example 8                                                                              90         87.5/360 84     slight mar;                               (comparative)                       some gloss loss                           ______________________________________                                    

Example 9

This example describes the preparation of a two component clearcoatcomposition containing the polysiloxane polyol of Example 1 at anadditive level. This clearcoat composition is curable at ambientconditions and suitable for automotive refinish applications. Theingredients of Component 1, which contains the polysiloxane polyol, andComponent 2, which contains an isocyanate curing agent, were co-blendedunder mild agitation just before spray application.

    __________________________________________________________________________                       Formula Weight                                                                        Weight Resin Solids                                Ingredients        (grams) (grams)                                            __________________________________________________________________________    Component 1                                                                   Methyl amyl ketone 8.28    --                                                 Xylene             8.75    --                                                 Flow additive.sup.1                                                                              0.34    0.17                                               Catalyst.sup.2     0.04    0.04                                               Ultraviolet light absorber.sup.3                                                                 1.01    1.01                                               Hindered amine light stabilizer.sup.4                                                            0.50    0.50                                               Polyester polyol resin as used in Example 8                                                      14.12   12.71                                              Acrylic polyol.sup.7                                                                             35.40   20.0                                               Polysiloxane polyol of Example 1                                                                 15.0    5.0                                                Methyl ethyl ketone                                                                              6.76    --                                                 Lactol spirits.sup.8                                                                             2.09    --                                                 Toluene            3.80    --                                                 Glycol ether acetate.sup.5                                                                       4.69    --                                                 VM&P Naphtha.sup.9 3.48    --                                                 2,4-Pentanedione   5.21    --                                                 Catalyst.sup.2     0.09    0.09                                               Component 2                                                                   Isocyanate curing agent.sup.6                                                                    50.50   50.50                                              Methyl isobutyl ketone                                                                           11.45   --                                                 Total              171.51  100.0                                              __________________________________________________________________________     .sup.1 Polyether modified dimethyl polysiloxane copolymer, commercially       available as BYK 300 from BYK Chemie USA.                                     .sup.2 Dibutyl tin dilaurate.                                                 .sup.3 2(2hydroxy-3',5ditert-amylphenyl) benzotriazole, commercially          available as TINUVIN 328 from CibaGeigy Corp.                                 .sup.4 Sterically hindered tertiary amine light stabilizer commercially       available as TINUVIN 123 from CibaGeigy Corp.                                 .sup.5 Propylene glycol monomethyl ether acetate commercially available a     ARCOSOLV PM ACETATE from Arco Chemical Co.                                    .sup.6 Hexamethylene diisocyanate trimer commercially available as HDTLV      from Rhone Poulenc, Inc.                                                      .sup.7 Formed from styrene, hydroxypropyl acrylate, isostearic acid,          glycidyl methacrylate and methyl methacrylate (32.4/23.3/22.4/11.2/10.7       weight ratio in xylene.                                                       .sup.8 Blend of low boiling aliphatic solvents from Ashland Chemical.         .sup.9 Blend of medium boiling aliphatic solvents from Ashland Chemical. 

Comparative Example 10

By way of comparison with Example 9, this example describes thepreparation of a two component clearcoat composition containing nopolysiloxane polyol at an additive level. The ingredients of Component 1and Component 2, which contains an isocyanate curing agent, wereco-blended under mild agitation just before spray application.

    ______________________________________                                                      Formula Weight                                                                             Weight Resin Solids                                Ingredients   (grams)      (grams)                                            ______________________________________                                        Component 1                                                                   Methyl amyl ketone                                                                          8.28         --                                                 Xylene        8.75         --                                                 BYK-300       0.34         0.17                                               Dibutyltin dilaurate                                                                        0.04         0.04                                               TINUVIN 328   1.01         1.01                                               TINUVIN 123   0.50         0.50                                               Polyester polyol used in                                                                    14.12        12.71                                              Example 9                                                                     Acrylic polyol used in                                                                      50.40        28.5                                               Example 9                                                                     Methyl ethyl ketone                                                                         6.76         --                                                 Lactol spirits                                                                              2.09         --                                                 Toluene       3.80         --                                                 Glycol ether acetate                                                                        4.69         --                                                 VM&P Naphtha  3.48         --                                                 2,4-Pentanedione                                                                            5.21         --                                                 Dibutyltin dilaurate                                                                        0.09         0.09                                               Component 2                                                                   HDT-LV        50.50        50.50                                              Methyl isobutyl ketone                                                                      11.45        --                                                 Total         171.51       93.52                                              ______________________________________                                    

APR24711 test panels were prepared by spray applying a pigmentedbasecoat commercially available as DELTRON DBU 9700 from PPG Industries,Inc. and allowing the basecoat to flash cure at ambient conditions for20 minutes. The clearcoat compositions of Example 9 and ComparativeExample 10 were then spray applied using conventional spray equipmentand allowed to cure at ambient conditions for one week prior to testing.

Panels were tested for 20 degree gloss, pencil hardness, adhesion,gasoline resistance and mar resistance. The 20 degree gloss was measuredas in Example 7; pencil hardness was measured in accordance with ASTMD3363-92a; adhesion was measured in accordance with ASTM D3359; gasolineresistance was determined as in Example 7. Mar resistance was determinedby marring coated panels with a wool felt cloth moving across anabrasive powder which has been applied to the surface of the coating.Gloss measurements are made on marred and unmarred areas and the marresistance is determined as percent retention of the original gloss. Thebasic apparatus for testing for mar resistance is an Atlas AATCC MarTester Model CM-5 available from Atlas Electrical Devices Company. Theabrasive powder which is used is commercially available Bon-Ami brand(Feldspar/Calcite). The Bon-Ami cleanser is applied to approximatelyone-half of the coated panel. Excess cleanser is removed so only a thinfilm of cleanser remains on the panel. Using the mar tester, thecleanser-coated panel is rubbed with a wool cloth ten times (10 doublerubs). After marring, the panel is washed with water to remove thecleanser, then the panel is dried with a paper cloth. The 20 degreegloss is measured in several places on both the marred and unmarredareas of the painted surface. The maximum and minimum gloss values aretaken and the mar resistance is determined as follows: ##EQU1## Thehigher the value, the better the mar resistance.

Results of the above-mentioned testing are reported in the followingTable 2.

                                      TABLE 2                                     __________________________________________________________________________    Clearcoat                                                                            20 Degree                                                                           Pencil                                                                             Adhesion                                                                             Gasoline                                                                           Mar                                             Composition                                                                          Gloss Hardness                                                                           (5 = 100%)                                                                           Resistance                                                                         Resistance                                      __________________________________________________________________________    Example 9                                                                            86    HB   5      No effect                                                                          86%                                             Example 10                                                                           86    HB   5      No effect                                                                          78%                                             (comparative)                                                                 __________________________________________________________________________

Example 11

This example describes the preparation of clearcoat compositionscontaining a polysiloxane and cured with an aminoplast curing agent.Compositions 11B, 11C and 11D contain various levels of the polysiloxanepolyol of Example 2 and a comparative clearcoat composition, 11A,contains no polysiloxane polyol. Primed panels were prepared by sprayapplying a pigmented basecoat commercially available as HWB-S-9517 fromPPG Industries, Inc., using conventional spray equipment and curing thebasecoated panels for 25 minutes at 285° F. (141° C.). The ingredientsof each clear coat composition were thoroughly mixed prior toapplication. Each composition was drawn down using a 10 mil draw barover the cured basecoat and the clearcoated panels were thermally curedfor 25 minutes at 275° F. (135° C.).

    __________________________________________________________________________             Composition                                                                   11A (grams)                                                                          Composition                                                                         Composition                                                                         Composition 11D                                   Ingredients                                                                            (comparative)                                                                        11B (grams)                                                                         11C (grams)                                                                         (grams)                                           __________________________________________________________________________    Methyl amyl ketone                                                                     3.0    4.1   5.1   7.3                                               Polysiloxane polyol                                                                    --     8.1   5.4   6.5                                               of Example 2                                                                  OH functional                                                                          10.8   1.6   3.3   --                                                acrylic.sup.1                                                                 Aminoplast curing                                                                      4.4    4.4   4.4   4.4                                               agent.sup.2                                                                   Polybutylacrylate.sup.3                                                                 0.07   0.07  0.07  0.07                                             Catalyst.sup.4                                                                          0.13   0.13  0.13  0.13                                             __________________________________________________________________________     .sup.1 Styrene/lauryl methacrylate/hydroxyethyl methacrylate/2ethylhexyl      methacrylate/methylacrylic acid/butyl acrylate/methylstyrene dimer polyme     (35:34.2:22:5.2:3.4:0.1:0.1), 60 per cent solids in xylene and mineral        spirits (95:5), with a hydroxyl equivalent weight of 591.6 based on resin     solids.                                                                       .sup.2 Commercially available as CYMEL 202 from Cytec, Inc.                   .sup.3 Flow control agent, 62% solids in xylene, molecular weight = 6700.     .sup.4 Phenyl acid phosphate.                                            

The cured test panels were tested for gloss and mar resistance asdescribed in Example 9. Results for these tests are reported in thefollowing Table 3.

                  TABLE 3                                                         ______________________________________                                                               Marred Gloss                                           Composition                                                                              20 Degree Gloss                                                                           (averaged) Mar Resistance                              ______________________________________                                        11A (comparative)                                                                        95.1        79.7       83.8%                                       11B        92.9         90.75     97.7%                                       11C        89.5        86.2       96.3%                                       11D        85.4        85.4        100%                                       ______________________________________                                    

Example 12

This example describes the preparation of a polysiloxane containing COOHfunctional groups, a product of the polysiloxane polyol of Example 2,with an approximate degree of polymerization of 3 to 4, i.e., (Si--O)₃to (Si--O)₄, and a polycarboxylic anhydride. The polysiloxane havingCOOH functional groups was prepared from the following mixture ofingredients:

    __________________________________________________________________________                   Equivalent  Parts By Weight                                    Ingredients    Weight                                                                              Equivalents                                                                         (grams)                                            __________________________________________________________________________    Charge I:      183.9 14.519                                                                              2670.0                                             Polysiloxane polyol of Example 2                                              Charge II:     154.0 14.519                                                                              2235.93                                            Hexahydrophthalic anhydride                                                   __________________________________________________________________________

To a suitable reaction vessel, equipped with a means for maintaining anitrogen blanket, Charge I was added at ambient temperature and heatedto 125° C. under a nitrogen blanket. Charge II was added dropwise, undermild agitation. Temperature was held at 125° C. to a stalled acid value,and the disappearance of anhydride as followed by IR spectroscopy.

A 50 percent by weight solution of the COOH functional polysiloxane inbutyl acetate was blended with an oxirane functional copolymer (glycidylmethacrylate, butyl methacrylate, styrene and methyl styrene dimer(60/30/7/2/1 weight ratio)) in a ratio of one equivalent acid to oneequivalent oxirane. To this resin blend was added 3 percent by weightbased on weight of resin solids of ethyl triphenyl phosphonium iodidecatalyst.

The resulting curable composition was drawn down with a 10 mil draw barover a cold rolled steel panel and cured at 220° F. (104° C.) for 30minutes. The cured coating was clear, glossy and colorless; having goodmar resistance and good solvent resistance to methyl ethyl ketone.

Example 13

This Example describes the preparation of clearcoat compositionscontaining relatively high molecular weight polysiloxane polyols andcured with an aminoplast curing agent. Primed cold rolled steel panelswere prepared by spray applying a pigmented basecoat commerciallyavailable from PPG Industries, Inc. as DCT-6373 using conventional sprayequipment and flash curing the basecoated panels for 10 minutes at 200°F. (93° C.). The ingredients of each of the clear compositions werethoroughly mixed prior to application. Each composition was sprayapplied using conventional spray equipment, flashed at ambienttemperature for 15 minutes before being baked at 285° F. (141° C.). for25 minutes. The cured clearcoats were measured for Distinctness ofImage, 20 degree gloss, mar resistance and acid etch resistance.Commercial clearcoats were also evaluated and the results are reportedIn Table 4 below.

The clearcoat formulation containing the polysiloxane polyols wasprepared by mixing together the following ingredients and reducing tospray viscosity (25 seconds, No. 4 Ford cup) with methyl amyl ketone:

    ______________________________________                                        Ingredients         Formula Weight (grams)                                    ______________________________________                                        SOLVESSO 100.sup.1  40.0       40.0                                           TINUVIN 328         3.0        3.0                                            TINUVIN 900         3.0        3.0                                            TINUVIN 123         1.2        1.2                                            TINUVIN 292         0.8        0.8                                            CYMEL 1130          70.0       70.0                                           Polybutylacrylate as in Example 11                                                                1.34       1.34                                           Diisopropylamine blocked dodecylbenzene                                                           6.66       6.66                                           sulfonic acid catalyst                                                        Polysiloxane polyol of Example 5                                                                  130                                                       Polysiloxane polyol of Example 6                                                                             130                                            ______________________________________                                         .sup.1 Blend of aromatic solvents available from Exxon Chemical Co.      

                  TABLE 4                                                         ______________________________________                                        Polysiloxane of             Mar      Acid Etch                                Example No.                                                                             DOI.sup.1                                                                             20° Gloss.sup.2                                                                  Resistance.sup.3                                                                       Resistance.sup.6                         ______________________________________                                        5         97      87.5      95.0%    7.5                                      6         98      80.3      47.9%    10                                       DCT 1002B.sup.4                                                                         97      91.6      73.2%    9                                        DCT 5002PSH.sup.5                                                                       86      83.3      21.2%    2.5                                      ______________________________________                                         .sup.1 Distinctness of Image (DOI) using a Dorigon II DOI meter. 100,         i.e., like a mirror.                                                          .sup.2 Measured as in Example 7.                                              .sup.3 Measured as in Example 9.                                              .sup.4 Acrylic polyolaminoplast cure clearcoat available from PPG             Industries, Inc.                                                              .sup.5 Epoxyacid cure clearcoat available from PPG Industries, Inc.           .sup.6 A solution of 298 parts deionized water and 15 parts of 0.2 N          sulfuric acid was prepared. The acid solution was spotted onto 2 ×      inch panels with a total of eight (8) spots, 50 microliters each. The         panels were then placed in an oven at 120° F. (49° C.) for      twenty minutes. The panels were removed from the oven and the spot/bake       procedure was repeated two more times to give a total of 60 minutes at        120° F. (49° C.).  # After the third cycle, the panels were     washed with soap and water and dried, then rated for acid etch resistance     on a scale of 0-10 based on standard test panels (0 = no observable etch;     10 = severe etching).                                                    

We claim:
 1. A curable composition comprising:(a) an organicpolysiloxane containing reactive functional groups, said polysiloxanehaving the following general structural formula: ##STR4## where m is atleast 1; m' is 0 to 50; n is 0 to 50; R is selected from the groupconsisting of H, OH and monovalent hydrocarbon groups connected to thesilicon atoms; R^(a) has the following structure:

    R.sub.1 --O--X

wherein R₁ is alkylene, oxyalkylene or alkylene aryl; and X is a moietycontaining a COOH functional group; and (b) an aminoplast curing agentor a polyepoxide curing agent, such that when the curing agent (b) is anaminoplast, the moiety X contains at least one COOH functional group andwhen the curing agent (b) is a polyepoxide, at least a portion of themoiety X contains two or more COOH groups.
 2. A curable compositioncomprising:(a) an organic polysiloxane, which contains reactivefunctional groups, said polysiloxane having the following formula:##STR5## where m is at least 1; m' is 0 to 50; n is 0 to 50; R isselected from the group consisting of H, OH and monovalent hydrocarbongroups connected to the silicon atoms; R^(a) has the followingstructure:

    R.sub.1 --O--X

wherein R₁ is alkylene, oxyalkylene or alkylene aryl; and X is a moietycontaining a COOH functional group; (b) a polymer or oligomer whichcontains reactive functional groups; and (c) an aminoplast curing agentor a polyepoxide curing agent, such that when the curing agent (b) is anaminoplast, the moiety X contains at least one COOH functional group andwhen the curing agent (b) is a polyepoxide, at least a portion of themoiety X contains two or more COOH groups.
 3. The curable composition ofclaim 2 wherein n+m and n+m' is 2 or
 3. 4. The curable composition ofclaim 2 wherein the curing agent is a polyepoxide.
 5. The curablecomposition of claim 2 wherein the organic polysiloxane is the reactionproduct of the following:(a) a polysiloxane polyol of the followinggeneral formula: ##STR6## where m is at least 1; m' is 0 to 50; n is 0to 50; R is selected from the group consisting of H, OH and monovalenthydrocarbon groups connected to the silicon atoms; R_(b) has thefollowing structure:

    R.sub.1 --O--Y

wherein R₁ is alkylene, oxyalkylene or alkylene aryl; and Y is H,mono-hydroxy substituted alkylene or oxyalkylene, or R₂ --(--CH₂--OH)_(p) wherein p is 2 or 3; and where R₂ is ##STR7## when p is 2 andR₃ is C₁ to C₄ alkyl, or R₂ is ##STR8## when p is 3, and (b) at leastone polycarboxylic acid or anhydride.
 6. The curable composition ofclaim 5 wherein (b) is an anhydride.
 7. The curable composition of claim6 wherein the anhydride is selected from the group consisting ofhexahydrophthalic anhydride, methyl hexahydrophthalic anhydride,phthalic anhydride, trimellitic anhydride, succinic anhydride, alkenylsuccinic anhydride, substituted alkenyl succinic anhydride, and mixturesthereof.
 8. The curable composition of claim 2 wherein the organicpolysiloxane is present in an amount of from 10 to 70 percent by weightbased on total resin solids of the coating composition.
 9. An organicpolysiloxane containing COOH functional groups which is the ungelledreaction product of the following reactants:(a) a polysiloxane polyol ofthe following general formula: ##STR9## where m is at least 1; m' is 0to 50; n is 0 to 50; R is selected from the group consisting of H, OHand monovalent hydrocarbon groups connected to the silicon atoms; R^(b)has the following structure:

    R.sub.1 --O--Y

wherein R₁ is alkylene, oxyalkylene or alkylene aryl; and Y is H,mono-hydroxy substituted alkylene or oxyalkylene, or R₂ --(--CH₂--OH)_(p) wherein p is 2 or 3; and where R₂ is ##STR10## when p is 2 andR₃ is C₁ to C₄ alkyl, or R₂ is ##STR11## when p is 3, and (b) at leastone polycarboxylic acid or anhydride.